For instance, in an automobile, work oil is employed for e.g. lubrication of an automobile engine, controlling of a hydraulically controlled device (a hydraulic control valve etc.). Such work oil is fed to respective parts of the automobile by an oil supply apparatus, and this oil supply apparatus includes a discharge amount varying arrangement capable of appropriately adjusting the discharge pressure of work oil in accordance with a rotational speed of the engine. An example of this type of oil supply apparatus is known from Patent Document 1 identified below.
The oil supply apparatus disclosed in Patent Document 1 includes a pump body having a suction port for suctioning work oil in association with rotation of a rotor which is driven in synchronism with a crank shaft as well as a first discharge port and a second discharge port that discharge work oil in association with the rotation of the rotor. In addition, this oil supply apparatus further includes a first oil passage for feeding at least work oil from the first discharge port to a work oil fed section, a second oil passage for feeding work oil from the second discharge port to the first oil passage, and a relief oil passage for feeding work oil from a hydraulic control valve including a valve body operable in response to oil pressure of the work oil to the first oil passage to at least one of the suction port and an oil pan.
In the oil supply apparatus described above, the valve body is provided with a first valve body oil passage and a second valve body oil passage. And, when the oil pressure of the work oil to the first oil passage is within a predetermined range, the work oil from the second discharge port is fed via the first valve body oil passage to the first oil passage; whereas when the oil pressure of the work oil to the first oil passage is above the predetermined range, the work oil from the second discharge port is fed via the second valve body oil passage to the first oil passage.
With the above arrangement wherein the work oil from the second discharge port can be fed via the first valve body oil passage to the first oil passage when the oil pressure of the work oil to the first oil passage is within the predetermined range, the feed amount of work oil to the first oil passage in this situation is the sum of the discharge amount of the first discharge port and the discharge amount of the second discharge port. As the rotational speed of the internal combustion engine increases and the rotational speed of the rotor increases, the amount of the work oil from the first discharge port alone becomes sufficient to ensure the necessary oil pressure. Then, it becomes unnecessary to combine the work oil from the first oil passage with the work from the second oil passage. In this case, the excess work oil in the second oil passage is returned to the relief oil passage without being fed to the first oil passage.
On the other hand, depending on the work oil fed component, feeding of a large amount of work oil becomes necessary when the rotational speed of the rotor is in a high speed range. For this reason, with this oil supply apparatus, the above-described arrangement is made such that when the oil pressure of the work oil to the first oil passage is above the predetermined range, the work oil from the second discharge port is fed via the second valve body oil passage to the first oil passage. In this, even after the feeding amount of work oil to the first oil passage consists of only the amount of work oil from the first discharge port, the feeding amount of work oil to the first oil passage can again comprise the sum of the discharge amount of the first discharge port and the discharge amount of the second discharge port. With this arrangement, even when the rotational speed of the rotor in a high speed range, it is still possible to increase the volume of work oil that can be fed, thus securing the necessary amount of oil to be fed to the work oil fed component.